A way to "tag" cache objects

I would like a way to tag a set of methods that I cache on arguments in the same identifier so that I can bulk invalidate them.

For example, I have a User who has a bunch of documents. If the user object changes, I want to invalidate the cache of all his documents. I don't want to be aware of all methods and their arguments they are cached at, I just want to say "invalidate bulk cache for user id 23" or something like that.